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Three-dimensional Computed Tomographic Angiography (3D CTA) is a new imaging technique for vascular structures. This study was aimed at investigating the diagnostic role of 3D CTA in the intracranial and extracranial arteries. Fifteen patients with intracranial artery disease (thirteen with aneurysms and two with arteriovenous malformations) and fifteen patients with stenosis of the common, internal or external carotid arteries underwent 3D CTA. All patients had been examined with intraarterial angiography. The CT examinations were performed with dynamic scanning during intravenous contrast agent administration. Three-millimeter thick contiguous slices were obtained in the cervical region and 1.5-mm contiguous slices in the intracranial region. CT findings were processed to produce 3D views on an independent workstation. 3D CTA results were compared with those of intraarterial DSA in all cases. Agreement was found in 13 of 15 cases of intracranial vascular abnormalities, and in 26 of the 30 carotid arteries in classifying the severity of the stenosis. The 3D views, which exhibit an excellent image quality, seem to be comparable to angiography in the intracranial and extracranial arteries. The main advantages of this technique are: 1) its low invasivity since only an intravenous contrast agent injection is required; 2) its easy and fast acquisition (2-3 minutes are needed if a non-spiral CT unit is used and less than one minute with spiral CT); 3) good demonstration of the calcified plaques which can be also removed with the softwares available at the workstation, to show the overall vessel lumen; 4) thanks to its simplicity the examination can also be performed in emergency (i.e. in patients with subarachnoid hemorrhage, if plain CT is positive for subarachnoid bleeding). Its main limitations are: 1) the need of an adequate concentration of contrast agent in the vessels; 2) artifacts due to calcified and bone structures; 3) no information about vessel inflow; 4) limited discrimination between arteries and veins in some areas (cavernous sinus); 5) limited field of view compared to angiography.

In order to assess the accuracy of CT and MRI in evaluating the local extent of rectal carcinoma, 22 patients with a rectoscopic diagnosis of rectal cancer were examined before surgery with both techniques. Tumor extent into the perirectal fat, involvement of surrounding structures and local adenopathy were evaluated on both CT and MR images. These findings were compared with the micro- and macrohistologic findings obtained from the surgical specimens. As far as perirectal fat infiltration is concerned, the diagnostic accuracy of CT was 73% and that of MRI was 71%. Sensitivity was 100% for CT and 91% for MRI, while specificity was low for both techniques (45% for CT and 50% for MRI). In evaluating local adenopathy, CT accuracy was 82% and MR accuracy was 90%, with 89% sensitivity for both techniques and 77% specificity for CT and 92% for MRI. The overall accuracy was 59% for CT and 67% for MRI. In agreement with literature data, our study shows a similar accuracy for CT and MRI in evaluating the local extent of rectal carcinomas. Moreover, our results confirm the value of macrohistology in the local staging of rectal carcinoma and its prognostic value, as well as the low specificity of both CT and MRI in evaluating lesion spread into the perirectal fat.